Buying used...

[FFGirl]

Hello everyone As mantioned in my other post I am being treated to a 28 gallon nano for my birthday on Friday....however I have stumbled across someone selling a full 90 gallon set up for less than what it will cost me to buy just my starter kit and stand. My question is, what are the red flags of buying used? And how well does a 90 gallon set up deal with a big move? It is full of fish, corals and inverts as well as live rock...Due to being a complete noob at this I of course do not already have a tank at home that I can have set up and waiting to recieve all of these living creatures....and I don't see how I could possibly move 90 gallons of water from the existing location....my big fear is that moving the live rock will cause significant die off leading to the death off all of his fish...Also, even if I was to go buy an RO DI unit that morning it will take too long to get it to make 90 gallons worth of good water so I would potentially have to use chemicals and tap water to get the thing filled FAST to all of the living things could get in there ASAP....advice from anyone???